CRUST-5.1 - A GLOBAL CRUSTAL MODEL AT 5-DEGREES-X-5-DEGREES

We present a new global model for the Earth's crust based on seismic r efraction data published in the period 1948-1995 and a detailed compil ation of ice and sediment thickness. An extensive compilation of seism ic refraction measurements has been used to determine the crustal stru cture on continents and their margins. Oceanic crust is modeled with b oth a standard model for normal oceanic crust, and variants for nonsta ndard regions, such as oceanic plateaus. Our model (CRUST 5.1) consist s of 2592 5 degrees x 5 degrees tiles in which the crust and uppermost mantle are described by eight layers: (1) ice, (2) water, (3) soft se diments, (4) hard sediments, (5) crystalline upper, (6) middle, (7) lo wer crust, and (8) uppermost mantle. Topography and bathymetry are ado pted from a standard database (ETOPO-5). Compressional wave velocity i n each layer is based on field measurements, and shear wave velocity a nd density are estimated using recently published empirical V-p-V-s an d V-p-density relationships. The crustal model differs from previous m odels in that (1) the thickness and seismic/density structure of sedim entary basins is accounted for more completely, (2) the velocity struc ture of unmeasured regions is estimated using statistical averages tha t are based on a significantly larger database of crustal structure, ( 3) the compressional wave, shear wave, and density structure have been explicitly specified using newly available constraints from field and laboratory studies. Thus this global crustal model is based on substa ntially more data than previous models and differs from them in many i mportant respects. A new map of the thickness of the Earth's crust is presented, and we illustrate the application of this model by using it to provide the crustal correction for surface wave phase velocity map s. Love waves at 40 s are dominantly sensitive to crustal structure, a nd there is a very close correspondence between observed phase velocit ies at this period and those predicted by CRUST 5.1. We find that the application of crustal corrections to long-period (167 s) Rayleigh;wav es significantly increases the variance in the phase velocity maps and strengthens the upper mantle velocity anomalies beneath stable contin ental regions. A simple calculation of crustal isostacy indicates sign ificant lateral variations in upper mantle density. The model CRUST 5. 1 provides a complete description of the physical properties of the Ea rth's crust at a scale of 5 degrees x 5 degrees and can be used for a wide range of seismological and nonseismological problems.